Along with the development of the IoT devices is the increase power supply for each device. However, not all the nodes are equipped with fixed power providers and have solar batteries. Thus, we need to find a solution to provide power to the nodes. The downlink power transfer and uplink information transmission protocol is one of the solutions to enable the IoT devices to harvest energy from source providers and switch to information transmission in the uplink phase on demand [1]}, [2]}, [3]}, [4]}, [5]}. That helps reduce the power consumption as well as the cables, wires for providing power. In [1]}, the authors designed a time-switching protocol for a RIS with the energy harvesting phase to charge the RIS capacitor and the signal reflecting phase to assist the transmission from the access point (AP) to the receivers. The AP's transmit beamforming, the RIS's phase scheduling and the passive beamforming were optimized to maximize the information rate. The resultant two sub-problems were solved following the conventional semidefinite relaxation method and monotonic optimization. In [2]}, the transmit precoding matrices of the BS and the RIS's passive phase shift matrix were optimized for maximizing the weight sum-rate of all information receivers in a power transfer scenarios.
